The present invention relates to a bump-height measuring method and a bump-height measuring apparatus, both for measuring the heights of projecting bumps formed on the surface of a work, and in particular, for measuring the heights of minute bumps formed on a circuit board, an LSI chip or the like, at a high speed and with high accuracy.
A light cutting method and a confocal method are well known as methods for measuring the heights of projections formed on the surface of an object.
The light cutting method is a method for emitting strip-shaped light onto the surfaces of projections, and determining the heights thereof from the amount of displacement of the emitted light between the surface of an object and the surfaces of the projections.
The confocal method is based on the following fact:
When light is emitted onto an object in such a manner as to form a spot on the surface of the object, then reflects from the object, and passes through a pinhole, the amount of light emitted onto a confocal point is the largest in an area onto which the light passing through the pinhole is emitted. To be more specific, according to the confocal method, the heights of projections are determined on the basis of the movement amount of a detection optical system or a work which is measured when the system or the work is moved vertically to detect a confocal point with respect to projections and a reference surface of the object.
If each of projections has a considerably small height of, i.e., several hundred microns, the above height measuring methods cause the following inconveniences:
The light cutting method, for example, needs to reduce the width of strip-shaped light to be emitted, and emit such strip-shaped light at a small angle with respect to an object to be measured. Further, it must increase resolving power for detecting displacement of the light as mentioned above. The confocal point method, for example, needs to decrease the size of the light spot of emitted light, and increase vertical movement-resolving power.
Moreover, the above height measuring methods have further disadvantages. For example, if tens of thousands of projections are dispersedly located in a large area, and their heights must be measured in a short time period, the following problems arise:
Each time the height of each of the projections will be measured, the object must be positioned with high accuracy, and light must be emitted onto each projection with high accuracy. Thus, the heights of the projections cannot efficiently be measured. In other words, they cannot be measured in a short time period.
In view of the foregoing, the object of the present invention is to provide a bump-height measuring method and a bump-height measuring apparatus, both for measuring the heights of projecting bumps formed on the surface of a work, at a high speed and with high accuracy.